Patent GB-675603-A (GB)
Title: Improvements in or relating to the separation of racemic amino acids
Inventor: NEUBERG CARL
IPC: C12P13/06
Filed: 1949-12-19
Abstract: The two enantiomers of a racemic amino acid are separated by a process which comprices acylating the racemic amino acid with a monocarboxylic acid or a residue thereof, dissolving the resulting acyl amino acid in an excess of solvent, adding an amidase to the solution, adjusting the pH of the solution to the optimum value for the action of the amidase, aseptically insulating the solution at the optimum temperature for the action of the amidase, neutralizing the acid released during incubation, maintaining the incubation until the optical rotation becomes constant and separating the amino acid in acyl form from the amino acid in free form, whereby separation of the two enantiomers is effected, the D-isomer constituting the acyl portion and the L-enantiomer constituting the free portion.  The preferred acylating agents are the lower aliphatic acids such as formic acid or acetic acids used in the form of the free acid or as anhydride or acid chloride.  The amidase used may be obtained from animals or from plants such as that from pancreatin or aspergillus oryzae. Commercial enzyme preparations may also be used.  Those specified include Clarase 900, Arthozym 10, Takadiastase, Crude enzyme, Phil-Protease, Pancreatin, and R and H 16, an excess of the enzyme beyond that which is necessary to split the acyl-L-isomer is used. The preferred temperatures vary according to the enzyme used but are usually between 37-50 DEG  C.  The pH also varies, but usually lies between pH 5 to pH 7.  Protection against infection may be effected by any aseptic liquid such as toluene.  The pH may be maintained constant during the hydrolysis either by the addition of alkali or by the use of a buffer salt.  The separation of the acylated and hydrolysed isomers is effected by solvent extraction using the differences in their solubilities.  Purification is effected by boiling to precipitate the enzyme and evaporation or extraction of the acid used in the acylation.  In examples: (1) D,L-tryptophane is acetylated buffered and incubated with Orthozym 10 under a layer of toluol.  The product is worked up as above after 10 days when the optical rotation had become constant; (2) D,L-methionine is benzoylated, buffered, incubated under toluol with Takadiastase, and worked up as above; (3) D,L-phenylalanine is formylated, buffered and incubated under toluol with Clarase 900; (4) D,L-tryptophane is formylated and treated as in example (2); (5) D,L-phenylalamine is acylated with phenylacetyl chloride, buffered, and incubated under toluol with orthozym 10; (6) D,L-isoleucine is formylated, buffered, and incubated with Takadiastase; (7) D,L-methionine is acylated and treated as in example (1); (8) D,L-aspartic acid is benzoylated and treated as in example (2); (9) D,L-lysine is dibenzoylated and then partially hydrolysed with hydrochloric acid to form the mono-benzoyl derivative which is treated as in example (2); (10) Lauryl-D,L-alanine is buffered, incubated under toluol and worked up as before; (11) Palmityl-D,L-alanine is treated as in example (10); (12) The acetyl-D,L-tryptophane used in example (1) is incubated with R and H 16 and worked up as before; (13) D,L-tyrosine is acylated with chloroacetyl chloride, buffered and incubated under toluol with clarase 900.